1. Field of the Invention
This invention relates to a rotary regenerator type ceramic heat exchanger with excellent resistivity against thermal shock, and more particularly to a rotary regenerator type ceramic heat exchanger of center hub support system to be supported at a central portion thereof so as to rotate about a central axis thereof.
2. Description of the Prior Art
In general, a rotary regenerator type ceramic heat exchanger of center hub support system of the prior art uses a well-known structure which comprises a hollow hub with a central shaft hole for receiving a rotary shaft, a cylindrical ceramic honeycomb structural body integrally joined to the outer circumference of the hub, and an annular reinforcing ring secured to the outer circumference of the honeycomb structural body. In a typical arrangement of the prior art, the rotary regenerator type heat exchanger rotates about the central axis thereof in a chamber which is divided into two sections insulated by a sealing material disposed therebetween. One half of the heat exchanger is heated by a hot fluid passing through one of the two sections of the chamber, and the thus heated half is rotated to the other section of the chamber so as to discharge the thus stored heat to a fluid to be heated in said other section.
The ceramic honeycomb structural body of the rotary regenerator type heat exchanger of the prior art has a shortcoming in that it is comparatively easily broken at the joint between the honeycomb structural body and the hub when exposed to thermal shock. More particularly, when the hot fluid passes through the channels of the ceramic honeycomb structural body surrounded by thin ceramic walls, the ceramic honeycomb structural body is heated to a high temperature. On the other hand, the hub at the central portion of the honeycomb structural body is comparatively thick and is not brought in contact with the hot fluid but kept in contact with metallic shaft having a high heat conductivity, so that the hub is kept at a low temperature. Accordingly, a steep temperature gradient is caused between the ceramic honeycomb structural body and the hub during the initial stage of using the heat exchanger, and such steep temperature gradient tends to result in a thermal shock which leads to breakage of the ceramic honeycomb structural body at the joint thereof with the hub.